Electric valve circuits



April 18, 1939. B BEDFORD 2,155,251

ELECTRIC VALVE CIRCUITS Filed Sept. 22, 1937 2 Sheets-Sheet 1 1] 1.Fig.1. tin

Inventor:

Burnice D. BedEO d, by WW6 X9 Hi5 Attorney April 18, 1939.

BL D. BEDFORD ELECTRIC VALVE G IRCUITS Filed Sept. 22, 1957 2Sheets-Sheet 2 Inventor: Buvnice D. Bedford,

. His Attorney.

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Patented Apr. 18, 1939 UNITED STATES ELECTRIC VALVE CIRCUITS I BurniceD. Bedford, Schenectady, N. Y., assignor to General Electric Company, acorporation 01' New York Application September 22, 1937, Serial No.165,143

11 Claims.

My invention relates to electric valve circuits and more particularly toexcitation or control circuits for electric valve apparatus.

In the control of electric valve apparatus where the apparatus isrendered conductive periodically upon the application of a suitablecontrol voltage to an associated control member, it has been found thatit is highly important to provide arrangements whereby the controlmember is energized in the desired manner during transient loadconditions or during transient disturbances. For example, in electricvalve systems such as inverter systems, it has been found that duringtransient conditions the voltages impressed on the control members varyconsiderably so that the electric valve means is not controlled in thedesired manner, resulting in many instances in very perceptiblevariations in output characteristics and in some instances ininterruption of service. There has been evidenced a decided need forauxiliary apparatus to be used in connection with the excitationcircuits for the electric valve means to assure positive and suitableenergization of the control members during the transient disturbances.

and assigned to the assignee of the present invention.

It is an object of my invention to provide a new and improved electricvalve circuit.

It is another object of my invention to provide new and improved controlor excitation circuits for electric valve apparatus.

It is a further object of my invention to provide new and improvedcontrol systems for electric valve apparatus in which there is assuredsuitable and positive energization of the control members of theelectric valves during transient load conditions or during transientdisturbances caused by extraneous conditions.

In accordance with the illustrated embodiments of my invention, Iprovide new and improved excitation systems for electric valveapparatus, particularly electric valve inverting apparatus. Although notlimited thereto, I have chosen to show my invention as applied toelectric valve apparatus used in a constant current direct currenttransmission system of the type disclosed and claimed in the abovementioned Stone patent. Suitable apparatus, such as rotatingdynamo-electric machines of the induction type, are connected across theterminals of the excitation circuits to supply to the excitationcircuits a balanced polyphase system of voltages during transientconditions. During normal operation of the electric valve system andduring the time in which a source of current for the excitation circuitsoperates normally, the dynamoelectric machine operates as a motorenergized from the source. Upon the occurrence of some irregularity orupon the occurrence of sudden application of load, efiecting anunbalance of the voltages of the source and causing a substantialreduction in the values of the voltage, the dynamo-electriomachineoperates as a generator to impress on the excitation circuits suitablealternating voltages, to assure positive and reliable control of theelectric valves during such disturbances.

In accordance with another embodiment of my invention, there is providedan excitation system for electric valves used in systems for effectingtransmission of energy between constant current alternating currentcircuits and direct current circuits. The excitation circuits of thesystem are energized from the constant current alternating currentcircuit and a dynamo-electric machine is connected across the terminalsof the excitation circuits to efiect application of suitable alternatingvoltages during transient conditions.

For a better understanding of my invention, reference may be had to thefollowing description taken in connection with the accompanying drawingsand its scope will be pointed out in the appended claims. Figs. 1, 2 and3 represent various modifications of my invention as applied to electricvalve systems for transmitting energy from a constant voltagealternating current circuit to a constant current direct currentcircuit,

or vice versa.

Referring now to Fig. 1 of the accompanying drawings, there isrepresented an embodiment of my invention as applied to an electricvalve translating system for transmitting energy between a constantvoltage alternating current circuit including conductors l, 2 and 3 andaconstant current direct current circuit 4 through electric valve means5l0. The electric valve means 5-H! are preferably of the type employingan ionlzable medium, such as a gas or a vapor, and each includes ananode II, a cathode l2 and a control member l3. To efiect transformationof the constant voltage alternating current to alternating current ofconstant value, or vice versa, I provide a suitable means such as amonocyclic network including a plurality of branches of seriallyconnected reactances of opposite sign, such as capacitances |4, I5 andI6 which are respectively connected in series relation with inductancesl1, l8 and I9. Each of the branches is connected across a differentphase of the constant voltage alternating current circuit includingconductors 2 and 3. As an agency for effecting proper voltagetransformation between the constant current circuits of the monocyclicnetwork and electric valves 5-|0, and for con necting the constantcurrent circuits to the electric valves, I employ a transformer 20having primary windings 2| and secondary windings 22, 23 and 24. Inorder to eifect an improvement in apparatus economy, I connect secondarywindings 22-24 to the constant current terminals of the monocyclicnetwork in the manner described and claimed in my copending patentapplication Serial No. 97,011, filed August 20, 1936 and assigned to theassignee of the present application. Excitation circuits 25-30,inclusive, are associated with electric valve means 5-|0, respectively,and serve to impress on the associated control members l3 alternatingvoltages to render the electric valves conductive in a predeterminedorder to effect transmission of energy between the constant currentcircuits and the constant current direct current circuit 4. Each of theexcitation circuits 25-30 is similar in construction and arrangement,and to facilitate description thereof excitation circuit 25 will beconsidered in particular. If it is desired to impress on the controlmember |3 an alternating voltage of peaked wave form, I may employ anysuitable arrangement such as a peaking transformer 3| of the saturabletype which has a core member 32 provided with a restricted saturableportion 33, a primary exciting winding 34 and a control winding 35 inwhich there is induced an alternating voltage of peaked wave form. Aparallel unidirectional conducting device 38 and a noninductiveimpedance, such as a resistance 31, may be connected in series relationwith the winding 35 and control member l3 to offer a relatively lowimpedance to the flow of normal control member current and to offer arelatively higher impedance to the flow of control current incident tothe deionization of the medium in electric valve 5. A capacitance 38 maybe connected between the control member I3 and cathode |2 to absorbextraneous transient voltages.

To impress on the control member l3 a negative unidirectional biasingpotential, I employ a self biasing type of circuit including a parallelconnected capacitance 39 and a resistance 40. The resistance 40 may beof a material having a nonlinear impedance-current characteristic, suchas the material disclosed and claimed in United States Patent 1,822,742granted September 8, 1931 on an application of Karl B. McEachron andassigned to the assignee of the present invention. The excitationcircuits are described in my copending application Serial No. 88,825filed July 3, 1936 and assigned to the assignee of the presentapplication.

Excitation circuits 25-30 may be energized from any suitable source ofalternating current of proper frequency, and in the arrangement shown inFig. 1 the excitation circuits are energized from the constant voltagealternating current circuit through a transformer 4| having primarywindings 42 and secondary windings 43. To adjust the phase of thevoltages impressed on the control members l3, any suitable arrangementsuch as a rotary phase shifter 44 may be interposed between the sourceof alternating current and the excitation circuits. As an agency forsupplying to the excitation circuits, during transient disturbances, apolyphase system of voltages, I have illustrated an energy storagedevice such as a dynamo-electric machine 45 which may be of theinduction type having stator or inducing windings 45 and having a rotormember 41. It is to be understood that the rotor may be of the woundtype or that the rotor may be of the squirrel cage type. To suppress ordiminish the intensity of the voltage disturbances which may be presentin the constant voltage alternating current circuit or which may bepresent in an auxiliary source when used, I provide suitable reactiveimpedances connected between the source and the excitation circuits andmachine 45. Resistances 49 may also be connected in series relation withthe inductances 48 to provide a net impedance of relatively high valueto prevent the transfer of appreciable energy from the dynamo-electricmachine 45 to windings 43 of transformer 4| during the occurrence oftransient disturbances in the constant voltage circuit.

The general principles of operation of the embodiment of my inventionshown in Fig. 1 will be explained when the electric translating systemthereof is operating to transmit energy from the constant current directcurrent circuit 4 to the constant voltage alternating current circuitincluding conductors 2 and 3. The electric valves 5-|0 are renderedconductive in a predetermined order and for predetermined recurringintervals of time, each substantially electrical degrees, to supplyalternating current of constant value to the monocyclic network throughtransformer 20, and the monocyclic network transforms the alternatingcurrent of constant value to constant voltage alternating current. Theexcitation circuits 25-30 are energized from the constant voltagecircuit, and the phase of the alternating voltages of peaked wave formimpressed on control members 3 may be adjusted by means of the rotaryphase shifter 44.

So long as the system operates in the regular or normal manner, thedynamo-electric machine 45 will operate as a motor energized from theconstant voltage circuit through transformer 4|. If, for example, due tosome irregularity of operation or because of a sudden application ofload, the polyphase system of voltages impressed on the excitationcircuit becomes unbalanced or decreases materially, the dynamo-electricmachine 45 will temporarily act as a generator to impress on theexcitation circuits a balanced polyphase system of voltages. Due to thepresence of the reactive impedances 48 and resistances 49, only a smallamount of the current supplied by the machine 45 will be transmitted tothe transformer 4| and the greater portion of the stored energy of themachine 4| will be utilized in supplying excitation currents to theexcitation circuits 25-30. In this way, the system responds to assurepositive and suitable excitation of the control members l3 of electricvalves 5-|0 even through the supply source for the excitation circuitstemporarily fails to effect proper energization thereof.

Fig. 2 represents another embodiment of my invention applied to anelectric valve translating system of the same general type shown in Fig.1, and corresponding elements have been as signed like referencenumerals. A constant current alternating current circuit, includingconductors 50, 5| and 52, is shown as being connected between themonocyclic network and the electric valves 5-! 0, and the excitationcircuit 28 for electric valve 8 is energized from the constant currentalternating current circuit through current responsive devices 53, 54,and 55 and a suitable phase shifting arrangement such as a rotary phaseshifter 56. The output circuit of the rotary phase shifter 56 supplies abalanced polyphase system of voltages through conductors 51, 58 and 59.Although only excitation circuit 28 for electric valve 8 is shown, it isto be understood that the excitation circuits for the other electricvalves are connected to conductors 51, 58 and 59 in the usual manner toeffect the proper energization of the respective control members. Thedynamo-electric machine 45 is connected across the output terminals ofthe rotary phase shifter 56 and serves to supply a balanced system ofpolyphase voltages in the event the constant current alternating currentcircuit departs or deviates from normal operation.

The operation of the arrangement shown in Fig. 2 will be brieflydescribed. The energization of excitation circuit 28 is obtained fromthe constant current alternating current circuit including conductors50-52 through the transformers 53-55 and phase shifter 56 which impresson exciting winding 34 of transformer 3| an alternating voltage. Duringtransient load conditions or during transient disturbances, if thecurrent in conductors 50-52 deviates from the normal mode of variationthe dynamo-electric machine 45 will act as a generator to impress onwinding 34 of transformer 3| a suitable alternating voltage of propermagnitude, thereby assuring proper energization of control member I3 ofelectric valve 8. Of course, the other excitation circuits (not shown)will be energized in like manner.

In Fig. 3 there is shown another embodiment of my invention as appliedto a system which is substantially the same as that shown in Fig. 1, andcorresponding elements have been assigned like reference numerals. Atransformer 60, having primary windings 6| and secondary windings 62, isconnected between the electric valves 5-I 0 and the monocyclic network.The elements of the arrangement of Fig. 3, where common to correspondingelements of Fig. l, have been assigned like reference numerals.

As an arrangement for energizing the excitation circuit 28 and the otherexcitation circuits (not shown) during transient conditions, I provide ahigh impedance network 63 connected between the stator windings 46 ofmachine 45 and the transformer 4|. The network 63 may comprise aplurality of branches of reactive impedances, such as capacitances 64,inductances 65 and may include adjustable resistances 66. The network 63suppresses or diminishes the transient voltage disturbances which may becommunicated to the transformer 4| from the constant voltage circuitincluding conductors l-3. Transformers 61, 6B and 69 are connected inseries relation with output conductors 10, H and 12 of rotary phaseshifter 44 to impress on the excitation circuits for electric valves.5-10 a polyphase system of alternating voltages derived from thedynamoelectric machine 45 during transient disturbances. Primarywindings 13 of transformers 61-69 are connected across the terminals ofwindings 46 of machine 45 and points of the adjustable resistances 66. I

The operation of the arrangement shown in Fig. 3 is substantially thesame as the arrangement shown in Figs. 1 and 2. During transientdisturbances of the system, the dynamo-electric machine 46 will operateas a generator to impress on the excitation circuits for electric valves5-10 a polyphase system of voltages to assure accurate and positivecontrol of the electric valves. The high impedance network 63 preventsthe voltage disturbances of the constant voltage circuit from beingreflected to the excitation circuits and also prevents an appreciableportion of the energy of the dynamo-electric machine 45 from beingtransferred to transformer 4|. Because of the mechanical and electricalstored energy of machine 45, the machine 45 responds to assureenergization of the excitation circuits dur ing transient voltagedisturbances and during temporary failure of the source of energization.

While I have shown and described my invention as applied to a particularsystem of connections and as embodying various devices diagrammaticallyshown, it will be obvious to those skilled in the art that changes andmodifications may be made without departing from my invention, and I,therefore, aim in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, a supply circuit, a load circuit, electric valvemeans connected between said circuits for transmitting energytherebetween, said electric valve means having a control member, anexcitation circuit comprising a source of alternating voltage forimpressing on said control member a control voltage, and energy storagemeans comprising a dynamo-electric machine for introducing into saidexcitation circuit an alternating voltage during transient conditions toassure energization of said control member during transient voltagedisturbances of said source.

2. In combination, a supply circuit, a load circuit, electric valvemeans connected between said circuits for transmitting energytherebetween, said electric valve means having a control member, asource of alternating voltage, an excitation circuit connected to saidsource for impressing an alternating voltage on said control member, andenergy storage means connected to said source and to said excitationcircuit and being arranged to receive energy from said source dur ingnormal conditions of operation thereof and being arranged to impress analternating voltage on said control member in event said source failstemporarily.

3. In combination, a supply circuit, a load circuit, electric valvemeans connected between said circuits for transmitting energytherebetween, said electric valve means having a control member, asource of alternating voltage, an excitation circuit having inputterminals thereof connected to said source and arranged to impress analternating voltage on said control member,

nating voltage for energizing said excitation circuit, and energystorage means comprising an alternating current dynamo-electric machineof the induction type connected across said excitation circuit and beingarranged to operate as a motor when said excitation circuit is energizedfrom said source and being arranged to supply alternating voltage tosaid excitation circuit during transient voltage disturbances of saidsource.

5. In combination, a constant voltage alternating current circuit, adirect current circuit, a constant current alternating current circuitconnected to said constant voltage circuit, electric valve meansconnected between said constant current circuit and said direct currentcircuit, said electric valve means having a control member forcontrolling the conductivity thereof, an excitation circuit for saidcontrol member, means energized in accordance with the current of saidconstant current circuit for impressing an alternating voltage on saidexcitation circuit, and a dynamo-electric machine connected to saidexcitation circuit and being arranged to operate as a motor when saidexcitation circuit is energized from said constant current circuit andbeing arranged to impress an alternating voltage on said excitationcircuit in the event the constant current circuit temporarily fails toenergize said excitation circuit.

6. In combination, a constant voltage alternating current circuit, aconstant current direct current circuit, means connected to saidconstant voltage circuit and comprising a plurality of seriallyconnected reactances of opposite sign for transforming constant voltagealternating current into alternating current of constant value, aconstant current alternating current circuit connected to said means,electric valve means connected between said constant current alternatingcurrent circuit and said direct current circuit, said electric valvemeans being provided with a control member for controlling theconductivity thereof, an excitation circuit for energizing said controlmember, a current transformer connected in said constant currentalternating current circuit for energizing said excitation circuit, anda dynamo-electric machine of the induction type connected to saidexcitation circuit and being arranged to operate as a motor when saidexcitation circuit is energized from said constant current alternatingcurrent circuit and being arranged to supply voltage to said excitationcircuit when said constant current alternating current circuittemporarily fails to enerize said excitation circuit.

7. In combination, an electric valve means having a control member, anexcitation circuit for said control member, a source of alternatingvoltage for energizing said excitation circuit, a high impedance networkconnected to said source, a dynamo-electric machine connected to saidexcitation circuit and connected to be energized from said sourcethrough said network, and means responsive to the voltage of saiddynamoelectric machine for introducing into said excitation circuit analternating voltage when the voltage of said source undergoes transientdisturbances.

8. In combination, an electric valve means having a control member, anexcitation circuit for energizing said control member, a source ofalternating voltage for energizing said excitation circuit, phaseshifting means interposed between said source and said excitationcircuit for controlling the phase of the alternating voltage impressedon said control member, a high impedance reactive network for absorbingvoltage transients of said source, a dynamo-electric machine of theinduction type connected to be energized from said source through saidnetwork, and means comprising a transformer connected to be energized inaccordance with the voltage appearing across terminals of said machineand points of said network for introducing into said excitation circuitan alternating voltage when said source fails temporarily.

9. In combination, an electric valve means having a control member, anexcitation circuit for energizing said control member, a source ofalternating voltage for energizing said excitation circuit, and energystorage means connected between said source and said excitation circuitfor supplying a periodic control voltage to said control member duringtransient disturbances of said source, said periodic voltage being ofsubstantially the same periodicity as said alternating voltage.

10. In combination, a polyphase alternating current circuit, a directcurrent circuit, a plurality of electric valve means connected betweensaid circuits for transmitting energy therebetween and each comprising acontrol member for controlling the conductivity thereof, a plurality ofexcitation circuits each associated with a different one of saidelectric valve means for rendering said electric valve means conductivein a predetermined order, a source of polyphase alternating voltage forenergizing said excitation circuits, and a polyphase dynamo-electricmachine connected between said source and said excitation circuits, saidmachine being arranged to operate as a motor energized from said sourceduring a normal operation of said source and being arranged to supply tosaid excitation circuits a balanced polyphase system of voltages in theevent the voltages of said source deviate from a normal mode ofvariation.

11. In combination, a polyphase alternating current circuit, a loadcircuit, a plurality of electric valve means connected between saidcircuits for transmitting energy therebetween, said electric valve meanseach having a control member, a plurality of excitation circuits eachassociated with a different one of said electric valve means forrendering said electric valve means conductive in a predetermined order,a source of polyphase alternating voltage for energizing said excitationcircuits, a polyphase dynamo-electric machine connected between saidsource and said excitation circuits and being arranged to operate as amotor during normal operation of said source and as a generator duringtransient disturbances of said source to supply to said excitationcircuits a balanced polyphase system of voltages during the transientdisturbance, and reactances connected in series relation with saidsource and said machine for limiting the energy transfer between saidmachine and said source during transient disturbances of said somce.

BURNICE D. BEDFORD.

